Electronically controlled injection system for an internal combustion engine



United States Patent Inventors:

Application No.: Filed:

Patented: Assignee:

Priority:

Wolfgang Reichardt Stuttgart-Rohr, Germany Wolf Wessel, Stuttgart, Germany June 26, 1968 Aug. 4, 1970 Robert Bosch GH Stuttgart, Germany March 28, 1968 Germany ELECTRONICALLY CONTROLLED INJECTION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE 16 Claims, 10 Drawing Figs.

US. Cl. 123/32, 123/139,123/119,123/140 Int. Cl F02d 5/02 Field of Search 32SPA, 32E, 3213-1, 119

[56] References Cited UNITED STATES PATENTS 3,051,152 8/1962 Paule etal 123/119 3,430,616 3/1969 Glockler et al 123/32X Primary Examiner- Laurence M. Goodridge Attorney- Michael S. Striker ABSTRACT: The injection time of one fuel injector may be made to overlap the injection time of a following fuel injector, even though only one multivibrator is used to control the beginning of all sequentially operated injectors. This is accomplished by causing storage means to charge during the time the multivibrator is in the unstable state, during which time current flows through the activation coil of a selected injector. 1

This storage circuit then discharges through the activation coil of the same injector when the control multivibrator changes state, thus causing current to continue to flow through the activation coil, thus in turn causing fuel to continue being injected by the injector.

8'1 ya n" Patented Aug. 4, 1970 3,522,794

Sheet 2 of 10 FIG.2

t m V A 4 INVENTORS Wolfgang REIC HARDT Rolf WESSEL WMM/ St mintheirATTORNEY Patented Aug. 4, 1970 Sheet T @L S m wi A I 1 1 1 I a .M m M w WW 1 u. v m n flw 1.3 m oqfwv 1 m WW: N w m T m n NJNNF in A 7 LII/1+ i :IFITIU, ms 2 m2 8 NM 3 ii. ll- W w w \w \w i wm mi 8 w R n n H 8 8 T i R m W 3 Q 3 u M m mm; 5 R am 2 W .N -M L H l 1 I Ii ll4 l| v ill; mm mm 5 m 071.1109! .Qrrlc'r their ATTORNEY Patented Aug. 4, 1970 3,522,794

Sheet of 10 INVENTORS Rolf WESSEL their ATTORNEY Wolfgang REICHAR DT 47L" 0 Mk Pr- .NNIA

Qm Nw mm mm m I i mom Patented Aug. 4, 1970 3,522,794

' Sheet 6 of 10 FIG. 6

( J l I l (ao F. 31) l (a2)-- r I (3205 V/A p3 (40) t t t5 3 (21) 6 t1 (24) Z //l (23) g //1 (22) V I L t4 INVENTORS Wolfnang REiCHARDT Rolf WESSEL BY I their ATTORNEY Patented Aug. 4, 1970 Sheet 7 of 10 T mm OAR M S EMS VE NRW m O a R H O w ihelr ATTORNEY Patented Aug. 4, 1970 Sheet 8 of 10 I I I I I I I I I I I l L ...J L

INVENTORS Wolfgang REICHARDT Rolf WE SSEL m 1. Sin-1 their ATTORNEY Patented Aug. 4, 1970 3,522,794

Sheet of 10 V// /A -l //////AL W 22 ////1 l7 ,/A l //L t INVENTORS Wolfgang REICHARDT Rolf WESSEL BY 7)]4710P/ .CfflrA/r their ATTORNEY FOR AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION This invention relates to electrically controlled fuel injection systems. In particular, it relates to electrically controlled fuel injection systems in which at least two injection means sequentially inject fuel into an engine at predetermined time instants in the operating cycle of said engine. More particularly, it refers to such systems wherein the injection time of all injectors is controlled at least in part by a single, monostable multivibrator, in such a manner that it is at least in part a function of at least one operating parameter of the engine.

In known arrangements of this type, as for example illustrated in U.S. patent No. 3,240,191, a single multivibrator has output pulses which, after amplification, are applied to the individual injection means in sequence by mechanical switching means which are activated synchronously with the distributor; In the operation of a six cylinder-four stroke internal combustion engine operating at 6000 revolutions per minute the maximum time available for each injection is 3.33 milliseconds (msec). Depending upon the loading, the actual injection time at these speeds varies between 1 msec and 3 mscc. In order to exercise effective control of the amount of fuel injected during the course ofsuch a short injection time, it is of course essential to keep the dead time of the injection means, which is a function of the time required to build up and destroy the magnetic field in the activation coil of the injector means, to a minimum. In these known injection arrangements, starting pulses, of for example 25 amperes, may be applied for the first 0.7 msec to insure rapid opening of the injectors, while for the remainder of the injection time the injection means is maintained open at a maintaining current of for example amperes. This conventional arrangement requires a relatively large amount of electronic circuitry within the control system, thus increasing the manufacturing costs. In addition, special precautions must be taken in setting up the injection system because of the high input power and the high peak currents which are required.

SUMMARY OF THE INVENTION It is an object of this invention to furnish a control system for fuel injection, in which the injection time of a given injec tion means may overlap the injection time of the following injection means, without requiring an individual control multivibrator for each of said injection means. The use of a single multivibrator in such an injection system is a very great advantage since, for efficient operation, it is necessary to regulate the amount of fuel injected in accordance with the then current operating parameters. Ifa single multivibrator is used for control, it becomes relatively, simple to convert the relcvant operating parameters into electrical signals, and to influence the time a monostable multivibrator is in its unstable state in proportion to said electrical signals. The injectors are then maintained open for a length of time depending on the length of time the monostable multivibrator is in the unstable state.

This invention thus comprises an electrically controlled fuel injection system in an engine having an operating cycle. It comprises at least two injection means adapted to inject fuel sequentially at predetermined time instants in said operating cycle, each for a length of time dependent upon the duration of an activation signal. Monostable multivibrator means, adapted to furnish first control signals at said predetermined time instants, said first control signals having a duration varying in response to at least one engine parameter are supplied. Further supplied are storage means, adapted to furnish an ad ditional control signal substantially at the end of each of said first control signals, each adapted to terminate at a time later than the termination of the corresponding first control signal in the operating cycle. Means are also provided for combining said first and additional control signals to form said activation signals, in such a manner that the beginning of each ofsaid ac tivation signals is dependent upon the beginning of said first control signals, and the termination ofsaid activation signal is dependent upon the termination of said additional control signal. Lastly, means are provided for applying said activation signals to each of said injection means at the corresponding time instant.

' The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram showing a first embodiment of an electrically controlled fuel injection system;

FIG. 2 is a timing diagram corresponding to the embodiment of FIG. 1',

FIG. 3 is a simplified circuit diagram of the embodiment shown in FIG. 1, using a single control multivibrator and two amplifying channels, each containing storage means;

FIG. 4 is a block diagram ofa second embodiment of a twochannel injection system, wherein each channel subdividcs into two branches. one for each injection means;

FIG. 5 is a block diagram of a system similar to FIG. 4, but having additional electronic switching means for applying the activation pulses to the individual injectors;

FIG. 6 is a timing diagram pertaining to the embodiment of FIG. 5;

FIGS. 7a and 7b is a circuit diagram of the embodiment of FIG. 5;

FIG. 8 is a block diagram for a fourth embodiment of the invention, particularly suitable for application in rotary piston engines;

FIG. 9 is a timing diagram for the embodiment of FIG. 8; and

FIG. 10 is a circuit diagram for the embodiment of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in FIG. I, the injection system in accordance with this invention is used in the operation of a four-cylinder, fourstroke internal combustion engine having a controlled ignition. Four switching means, 11, I2, 13 and 14, are located in the distributor and are activated by switching cams rotating at cam shaft velocity and adapted to cause each switching means to remain open for approximately one-halfa revolution and to remain closed for the remainder of the revolution. As shown in FIG. 2, switching means or, here,

' simply a switch. 11, may close at time t,, switch 14 at t or,

degrees of cam shaft rotation later, switch 13 at t or after half a revolution has elapsed. and switch 12 at t,, or after approximately 270 degrees have passed since the closing of switch 11. Switch 11 opens shortly before the closing of switch 13 or at approximately degrees of cam shaft rotation, and the other switches in turn remain closed for 170 degree rotation following their respective closing times.

The injection system comprises four elcctromagnetieally operated injection means, shown as injectors 21-24 in FIG. l. The ignition order is assumed to be I. 4. 3, 2. Injector 2I is assumed to correspond to cylinder 1, and has an activation coil connected in series with switch 11. Injector 23 is assumed to correspond to cylinder 3 and has an activation coil connected in series with switch 13. Both of these injector activation coils are connected to the output of a first amplification channel. The remaining injectors 22 and 24 have activation coils respectively connected in series with switches 12 and I4 and are connected to the output of a second amplification chan nel. A single control multivibrator 33 furnishes first control signals, here rectangular first control pulses, to both of these channels. The duration of these first control pulses s at least in part a function of an operating parameter of the internal combustion engine 10. This functional dependence is indicated by the broken line in FIG. 1. If fuel is furnished to the injectors under constant pressure, as for example twice atmospheric pressure, the amount of fuel injected per injection time by each injector is obviously a function of the time duration of injection for each injector, and thus a function of the duration of the first control pulses.

Each of the switches 11-14 must be connected to the single control multivibrator in such a manner that the monostable multivibrator is switched to the unstable state for each operation (here closing) of any of the switches. As is shown clearly in FIG. 1, the switches are connected to a bistable multivibrator, 32, in such a manner that sequentially operated switches switch said bistable multivibrator from one stable state to the other stable state. Each stable state results in activation of a corresponding channel by use of AND gates 34 and 39, respectively, These gates furnish first and second AND output signals, respectively, when an input is present at both input terminals of the respective AND gate. Thus, AND gate 34 will generate a first AND gate output signal when bistable multivibrator 32 is in the first stable state and control multivibrator 33 is in the unstable state. Similarly, AND gate 39 generates a second AND gate output signal when bistable multivibrator 32 is in the second bistable state and the control multivibrator is in the unstable state. lt thus becomes obvious that switches 11-14 in conjunction with bistable multivibrator 32, which is one embodiment of bistable circuit means, and AND gates 34 and 39 together constitute means for applying the activation signals to corresponding injection means at the predetermined time instants of the operating cycle.

In dependence on the first and second AND output signal respectively, storage means 35 and 40 are charged. Upon termination of said respective AND output signals, the corresponding storage means begin to discharge, yielding respective additional control signals. Means for combining corresponding first control and additional control signals are shown at 36 and 41 respectively. These may for example be OR gates, which will yield an output when an input appears at either input terminal. Thus, activation signals, or signals whose beginning depends on the beginning of the first control signal and whose termination depends upon the termination of the additional control signal, will appear at the outputs of gates 36 and 41 respectively. These may be amplified by amplifiers 51 and 52 and then applied to corresponding injection means. Which ofthe two injectors in each channel will receive a particular activation signal is of course determined by which switch is closed.

Referring now to FIG. 2, a detailed example of the operation of this embodiment is as follows: Switch 11 closes at time t,, causing bistable multivibrator 32 to assume the first stable state, thus furnishing one input to AND gate 34. Simultaneously, control multivibrator 33 is switched to the unstable state, thus causing a first AND output signal to appear. This causes storage means 35 to charge, and also causes the beginning of the activation signal to appear at the output of OR gate 36. The activation signal is amplified by means of amplifier 51 and applied to the activation coil of injector 21. At time t which is determined in part at least by an operating parameter of the engine, the control multivibrator returns to the stable state. Starting at time t storage means 35 discharges, causing the output at OR gate 36 to continue. Thus, injector 21 remains open until the additional control signal, caused by the discharge of the storage means, terminates. This occurs at time t in FIG. 2. It should be noted that time t must of course precede the opening of the switch 11. Otherwise, control of the de-activation of injector 21 would pass to switch 11. In this example the total injection time, or duration of the activation signal, was thus the sum of the first control signal time 7] added to the time 1 of the additional control signal. lt should further be noted that in this particular example the time 'r. of the additional control signal was dependent upon the time "r, of the first control signal, since the storage means charged during the time 1,. If, as shown in FIG. 2, both charge and discharge are linear, the time of the additional control signal may be made proportional to the time of the first control signal.

At time t the next switch in sequence, namely switch 14, is closed. Bistable multivibrator 32 assumes its second stable state, and AND gate 39 generates the second AND output signal for the duration of which the control multivibrator, which has been switched to the unstable state again, is in said unstable state. The second AND output signal is applied to OR gate 41, amplified in amplifier 52 and applied to injector 24, since switch 14 is closed. The duration of the first control pulse is 1,, and the monostable multivibrator returns to the stable position at time t Similarly to the process described above, storage means 40, charged during time t to t,- and now discharges until time t,,. The activation pulse appearing at the output of OR gate 41 is of a duration corresponding to the sum of the durations of the first control pulse and the additional control pulse, r, and T2, respectively. At time t,,, upon discharge of the storage means, which again must precede the opening of switch 14, the injector 24 is de-activated.

Since switch 11 has opened a short time previously, closing of switch 13 at time t,-, causes bistable multivibrator 32 to be switched back to the first bistable state. Exactly the same operation as described in conjunction with the closing of switch 11 then ensues, except that the activation signal is ap plied to injector 23, since switch 13 is closed. The end of the activation signal, and thus the end of injection by injector 23, again occurs after a time period T: 1,, from the beginning of the activation signal, or closing of switch 13. Injector 22, corresponding to cylinder 2, is last in the injection operating cycle. It is activated at a time t, corresponding to closing of switch 12, exactly in accordance with the operation previously described in relation to injector 24. At the termination of the injection by injector 22, the full operating cycle is ready to repeat.

The circuit diagram corresponding to the embodiment of FIG. 1 is shown in FIG. 3. Here, bistable multivibrator 32 is embodied in transistors 135 and 138. Control multivibrator, a monostable multivibrator, 33 is embodied in transistors 165 and 168. AND gate 39 is embodied in transistor 95, Storage means 40 are embodied in transistors 97, 103, and 107. OR gate 41 is embodied in transistor 113 and amplifier 52 in transistors 115 and 118,

Transistors and 147 are merely decoupling transistors and do not serve any logic function.

In conformance with the operation described in relation to FIG. 2, the operation of the various elements of FIG. 3 is as follows:

At time t,, shortly following the opening of switch 13, switch 11 closes. Decoupling transistor 125, which is connected preceding bistable multivibrator 32, is switched to the conducting state via resistor 122. The positive voltage step resulting at the collector of this transistor is differentiated by a condenser 128 and resistor 129 and controls transistor via diode 132. Thus, transistor 135 becomes conductive for a short time period switching bistable multivibrator 32, causing transistor 135 to remain conductive. The negative step at the collector of transistor 135 is differentiated by second differentiating means consisting of capacitor 154 and resistor 153. This causes the control multivibrator 33 to switch to the unstable state. The time during which the control multivibrator will remain in the unstable state, corresponding to the time of the first control signal, is here determined by an inductive time constant member in the form of a transformer 167. The inductivity of transformer 167 may be made dependent on the intake pressure in the conventional fashion.

Since both transistor 135 and transistor 168 are now conductive, transistor 85, which serves as AND gate 34, does not receive any base current. It is thus blocked. The voltage at its collector assumes then a value which is substantially determined by the size of resistors 86 and 70 and is approximately equal to one-half the supply voltage supplied over supply voltage lines 5 and6. Transistor 65 becomes conductive via resistance 70, thus causing transistors 63 and 60 to become conductive also. Injector 21 begins injecting. Simultaneously, capacitor 83, belonging to storage means 35, is charged by means of a constant current source, which, in the example shown, consists of transistor 84 and resistor 79.

After the time 1",, corresponding to the durationof the first control signal, control multivibrator 33 returns to the Stable state. This causes transistor ,85 to become conductive via resistor 89. The negative voltage step resulting at the collector of transistor 85 is applied to the base of transistor 76 by means of the base-collector diode of inversely operated transistor 84, and also by means of capacitor 83. Transistor 76 thus blocks. Transistor 65 remains conductive, drawing current through resistors 75 and 71. Injector 21 remains open.

Capacitor 83 discharges with substantially constant current over a series connection consisting of transistor 77 and re sistor 78. The linear charging and discharging of condensor 83 causes the discharge time r or time corresponding to the additional controlsignal to be proportional to the duration of the first control pulse, -r,. However, any desired relationship between 'r and 'r, may be achieved by appropriate manipulation of the charge and discharge characteristic of capacitor 83. In particular, the relationship of the time duration of the first control pulse and of the additional control pulse may also be made dependent upon an operating parameter of the engine, or any other preselected parameter. After expiration of the time T capacitor 83 has discharged, and transistor 76 again becomes conductive. No base current is now received by transistor 65 over either resistance 70 or 71, thus causing this transistor to block. This in turn causes transistors 63 and 60 to block and injector 21 returns to the closed position.

Switch 14 is closed at time t causing transistor 147 to become conductive and causing bistable multivibrator 32 to assume the second bistable state, in which transistor 138 is conductive and transistor 135 is blocked. Control multivibrator 33 is again switched to the unstable state, via capacitor 155. Transistor 85 remains conductive over resistors 136 and 88, while transistor 95 is blocked, while transistor 113 becomes highly conductive over resistors 96 and 109. This causes transistors 115 and 118 to become conductive and injector 24 is activated. Capacitor 98 is charged by constant current source consisting of transistor 97 and resistor 99.

After expiration of the time T the control multivibrator 33 returns to the stable state, and transistor 95 becomes conductive. Transistor 107 blocks during the time T in which capacitor 98 is discharged at a constant current over transistor 103 and resistor 105. During this time transistor 103 remains conductive as do transistors 115 and 118. Injector 24 remains open during this time.

When, after the time T the duration of the activation signal has expired, transistor 107 becomes conductive, and transistor 113 blocks. Transistors 115 and 117 also block, and injector 24 is de-activated.

The activation of injector 23 begins at time t in a manner similar to that described in relationship to injector 21 at time t,. Injector 23 is thus energized over first AND gate 34 (transistors 85), first storage means 35 (transistor 84, 77 and 76), first OR gate (transistor 65) and first amplifying means 51 (transistors 63 and.60). ltis maintained open for the duration of the activation signal, which comprises the sum of the first control signal time 1, plus the additional control signal time T2. In a similar manner, injector 22 is subsequently energized via the second AND gate, storage means, OR gate and amplifying means.

Reference to FIG. 2 will show that, in accordance with. the present invention, it is possible to continue the fuelinjection by any injector for a time period overlapping the injection by the subsequent injector. For example, for the case illustrated in FIG. 2 which represents the operation of a four-cylinder, four-stroke combustion engine, the fuel injection time by each injector can exceed 360/4 90 degrees of cam shaft rotation.

' This can be accomplished even though only one control multivibrator is used. It should be noted that the control multivibrator illustrated in the Figure represents a great simplification of the actual control multivibrator. A further simplification was achieved by allowing switches 11, 12, 13 and 14 to set the control multivibrator 33 as well as to accomplish the distribution of the activation pulses to the individual injectors synchronously with the spark distribution. Because these switches perform these two functions, the longest activation time for any given injector is limited to the longest time one of these switches may remain closed, in spite of the division of the system into the two channels. Because of the time required for switching the bistable multivibrators from one stable state to the other, the amount of time any one of the switches may remain closed is somewhat shorter than the largest theoretical time, which corresponds to 180 degrees of carn shaft rotation.

Another variation of the basic idea of this invention may consist of supplying individual storage means for each individual injector, while still using only one monostable control circuit. In this case, it is necessary to furnish suitable distribution means between the monostable control circuit and the individual storage means. These distribution means may take the form of logic circuits. Such an arrangement may prove particularly advantageous for engines in which the amount of fuel to be injected varies greatly from one operating cycle to the next. In this way, it is possible to achieve the highest possible fuel injection quantity by causing the additional control pulses to maintain each injector open beyond the beginning of the subsequent first control pulse, thus maintaining the injectors open continually. This maximum fuel injection quantity can thus be achieved while still maintaining the possibility of the smallest opening time which, for constructive reasons, lies in the range of approximately one millisecond.

In the first embodiment described above, it may be inconvenient that each injector must have two cable connections. This is avoided in the second embodiment as shown in FIG. 4 in which each injector 21, 22, 23 and 24 is connected to ground on one side.

The injection system pictured in block-diagram form in FIG. 4 is also a two-channel system, which is activated by four switches 11, 12, 13 and 14 which in turn are activated at degree cam shaft spacings. Each of these switches remained closed for approximately degrees of cam shaft rotation. However, the activation current of the injectors does not pass through the contacts of these switches, which are required to carry only the relatively low current required for the operation of one of first, second, third or fourth additional AND gate 37, 38, 42 and 43. AND gates 37 and 38 respectively thus cause the proper distribution of the activation pulse generated by OR gate 36 to injectors 21 and 23 respectively, while AND gates 42 and 43 accomplish the proper distribution of the activation signal generated by OR gate 47 to injectors 24 and 22 respectively. In particular, AND gate 37 has a first and second input respectively connected to OR gate 36 and switch 11, and an output connected to amplifying means 51 which feed injector 21. AND gate 38 is connected both to OR gate 36 and switch 13, has an output connected to amplifying means 53 which furnish the signal for injector 23. Since AND gates have an output only when signals appear at both inputs, it is obvious that injector 21 will be energized only for the time that switch 11 is closed and for the duration of the activation pulse, while injector 23 will be energized during the time switch 13 remains closed and for the duration of the activation signal. Similarly, in the second channel, AND gate 42 has one input connected to switch 14 and a second input connected to OR gate 41, the second OR gate, while AND gate 43 has one input connected to switch 12 and a second input connected to OR gate 41. Amplifying means 54 cause the amplified output of AND gate 42 to be applied to injector 24, while amplifying means 52 cause the amplified output of AND gate 43 to be applied to injector 22. In all other respects the operation of the circuit according to FIG. 4 is identical to that shown in FIG. 2.

lt should be noted that in the embodiment of FIG. 4 it is also possible, by use of a bistable multivibrator which is switched to the opposite stable state for each sequential closing of one of the switches 11, 12, 13 and 14, that only two storage means are used, even though the injection system contains four channels, one for each of the injectors.

In the above-described embodiments, it was assumed that the ignition order of the four-cylinder engine to be energized by the injection system was l-4-3-2. Thus, the injectors were operated in the order 21, 24, 23 and 22. If, however, the ignition order for the cylinders is 1-3-4-2, it would be possible to use the above-described injection systems by letting injector 24 correspond to the third cylinder and injector 23 to the fourth.

The same injection system could also be used for eightcylinder engines, by connecting a second injector namely one of the injectors 25-28, in parallel with the first injectors 21-24. Thus, for an engine having an ignition order 1-5-4-8-6-3-7-2, injector 25, corresponding to the fifth cylinder, could be opened and closed simultaneously with injector 21 which pertains to the first cylinder, but at a time period sufficiently in advance of the ignition time of the first cylinder. Similarly, injector 28, corresponding to the eighth cylinder, may be operated together with injector 24, corresponding to the fourth cylinder, injector 26, corresponding to the sixth cylinder, simultaneously with injector 23 corresponding to the third cylinder; injector 27, corresponding to the seventh cylinder, simultaneously with injector 22, corresponding to the second cylinder. Any other of the various ignition orders of internal combustion engines may be realized in this way, merely by connecting together in pairs those injectors corresponding to two cylinders immediately following each other in the ignition sequence.

The same is true for the third embodiment which will be described below in connection with FIGS. -7, which is illustrated for a four-cylinder engine having an ignition sequence 1-4-3-2, but which may be used, as described above, for an eight-cylinder engine also.

The third embodiment differs from the first two embodiments in that the switches 1-14 do not serve the double function of determining the beginning of the activation signal and the distribution of the activation signal. In the third embodiment, the distribution of the activation signal is accomplished electronically. As shown in FIG. 5 in addition to the bistable multivibrator 32, which was present in the first embodiments, there is furnished first additional bistable circuit means numbered 30 and second additional bistable circuit means numbered 31. In the Figure, first additional bistable circuit means 30 are assumed to be an additional bistable multivibrator which is adapted to be switched to a first bistable state by the closing of switch 11, and to a second bistable state by the closing of switch 13. When multivibrator 30 is in the first bistable state, it is adapted to generate a first additional bistable output signal which is applied to AND gate 37, while in the second bistable state it is adapted to generate a second additional bistable output signal which is applied to the input of AND gate 38. Similarly, bistable multivibrator 31 is switched to a first bistable state by closing of switch 12, and to a second bistable state by the closing of switch 14. The corresponding generated output signals are the third and fourth additional bistable output signals, which-are respectively applied to the inputs ofAND gate 42 and AND gate 43. By addition of these two additional bistable multivibrators, it has thus been accomplished that the activation pulse (output of AND gates 37-43) applied to each injector is independent of the actual closing time of switches 11-14. The construction of the switches is simplified greatly, since bouncing of the switches, intermittent contact, etc., is no longer of importance. The only importance of the switches is to assure satisfactory contact at times t L t;, and t,.

As shown in the timing diagram of FIG. 6, multivibrator 30 is switched from the second bistable state to the first bistable state at time t,, and remains in this state until the beginning of the activation signal for injector 23 which takes place at time t;, by closing of switch 13. However, at time t multivibrator 30 also switches bistablemultivibrator 32 which in turn switches control multivibrator 33. The latter is switched into the unstable state, whose duration 1', is determined at least in part by the operating parameters of the engine. Simultaneously, storage means 35 are charged and therefore can furnish an additional control pulse of duration 7 at the end of the first control pulse which takes place at t The duration of the activation pulse is thus from t to t,,. The time t may follow the time t in the operating cycle, where t is the time of activation of the following injector. This has already been described in detail for the injection systems of the previous embodiments.

The circuit diagram of FIG. 7, corresponds to an injection system pictured in the block diagram of FIG. 5. Similarly to the diagram of FIG. 3, the system shown in FIG. 7, has a first channel starting at the center of the top row of FIG. 7, consisting of identical elements AND gate 34, storage means 35, OR gate 36. In FIG. 7, however, the output of OR gate 36 is applied to one input each ofAND gates 37 and 38. The output of AND gate 37 is then applied to injector 21 by means of amplifier 51, while the output of AND gate 38 after amplification in amplifier 53 is applied to injector 23. To simplify the explanation, the second channel is shown in FIG. 7 starting at the middle and extending towards the right. It consists of AND gate 39, storage means 40 and OR gate 41. Output of OR gate 41 is applied to inputs of AND gates 42 and 43. The outputs of the AND gates are, after amplification in amplifiers 54 and 52, applied to injectors 24 and 22 respectively. The circuits for AND gates 37, 38, 42 and 43 may be identical. Thus, AND gate 37 may consist of an npn transistor 201 having a collector resistance 202. The base of transistor 63, belonging to amplifying means 51, is connected to the collector of transistor 201. Two coupling resistors 203 and 204 are also connected to the base of transistor 201, one of which is connected to the collector of transistor 65 which belongs to OR gate 36. The other coupling resistor 203 is connected to the collector of transistor 235 which, together with transistor 231, forms the bistable multivibrator 30. The bases of transistors 231 and 235 are respectively connected to switches 11 and 12. For example, upon closing of switch 11, transistor 231 blocks and remains blocked until the closing of switch 13 causes transistor 235 to block.

AND gate 38, corresponding to injector 23, is also connected to the same bistable multivibrator 30. However, transistor 205, belonging to AND gate 38, is connected to the other output of multivibrator 30 by means of its coupling resistance 207. In particular, this transistor is connected to the collector of transistor 231. The second coupling resistor 208 of AND gate 205 is connected together with the coupling resistor 204 of AND transistor 201 to the collector of transistor 65, belonging to OR gate 36.

In accordance with the symmetry of the system which is so clearly recognizable in FIGS. 5 and 7, base resistor 213 of transistor 211 (belonging to AND gate 42) is connected with the collector of transistor 245, whose base may be short-circuited by means of switch 14 and which may then be maintained in the blocked condition by means of transistor 241, since transistors 241 and 245 jointly constitute the additional bistable multivibrator 31. The other coupling resistor 214 of AND gate transistor 211 is connected to the collector of transistor 113 which serves as OR gate 41. Also connected to this collector is the corresponding coupling resistor 218 of transistor 215 which belongs to AND gate 42. The second coupling resistor 217 of transistor 215 is connected to the collector of transistor 241 which is part of bistable multivibrator 31. The base of transistor 241 is connected to switch 12, which is the last to close in accordance with the ignition sequence 1-4-3-2.

For each change of state of multivibrators 30 and 31, the common bistable multivibrator 32 is switched from one bistable state to the next bistable state by means of capacitors 128, 328 or 144, 344 and one of the diodes 132, 332 or 142, 342 respectively. The multivibrator 32 is identical to that shown in FIG. 3 with the same reference numeral except for the use of these double inputcircuits. lt switches control multivibrator 33 to the unstable state in synchronism with the closing of switches 1l-l4.

While, in the embodiments of this invention so far described, four injectors are operated in sequence within each operating cycle of the engine, the fourth embodiment, shown in FIGS. 8-10, shows an injection arrangement having only two injectors or groups of injectors which are operated alternately and wherein each injection is terminated only after the beginning of the injection ofthe other injector or group of injectors respectively. This type of arrangement is particularly useful in rotary piston motors, whose pistons have a triangular cross-section with convex sides and rotate in a housing whose interior forms an oval curve. having necked-in sections in the vicinity of the location of the spark plugs (epitrochoids). The three corners of the piston always touch the walls of the housing during rotation, so that three separate work chambers result which increase and decrease periodically, are mutually separated, and are mutually displaced one from the other by 120 degrees in the direction of rotation. These serve to suck in the air-fuel mixture in passing the intake pipe. Because of the absence of reciprocating masses, very high rotational speeds may be achieved. For such high speeds, insufficient time would be available to carry through the required three injections per piston rotation with a single controlled injector. The problem is further complicated by the fact that the no-load rotational speed is very low for these motors, thus requiring control of very small fuel quantities and it is therefore impossible to increase the amount of fuel injected by the injector within a unit time by for example increasing the pressure or increasing the diameter of the intake piping.

To achieve the desired operation of a rotary piston engine, the injection arrangement comprises two injectors 21 and 22 situated in the intake pipe of the engine and two switches 11 and 12 respectively corresponding to injectors 21 and 22. As shown in FIG. 9, the closing time instants t,, t and t, are mutually displaced by a rotational angle of 120 degrees of the motor piston, so that switch 11 closes at t,, switch 12 at t and switch 11 again at t As shown in the block diagram of FIG. 8, the switches are directly connected to two inputs of the bistable multivibrator 32. Thus, the bistable multivibrator 32 is switched into the opposite stable state for each closing of one of the switches and in so doing switches control multivibrator 33 to the unstable state. Storage means 35 are charged during the time T ofthe control pulse duration, which depends on the operating parameters of the motor as discussed above. As discussed in detail above, the additional control pulse furnished by the discharge of the storage means causes an ac tivation signal to be applied to injector 21 whose duration is equal to the sum T, 1- of the first control pulse duration plus the additional control pulse duration. If necessary, for example for high rotary speeds or at high loads, the duration of this activation pulse may cause the injection time of injector 21 to overlap the beginning of the injection of injector 22 as shown in FIG. 9.

The individual circuits shown in FIG. 10. are substantially equal to the circuits shown in FIG. 3. The control circuit leading to injector 21, and consisting of AND gate 34, storage means 35, OR gate 36, and amplifier 51, is constructed identically to that shown in FIG. 3, as is the control circuit leading to injector 22 which consists of AND gate 39. storage means 40, and OR gate 41 with amplifier 52. However, the circuitry of bistable multivibrator 32 may be simplified considerably by connecting switches 11 and 12 directly to the bases of transistors 135 and 138 respectively. Control multivibrator 33 is identical to that used in the other embodiments of this invention. As stated above, it is switched in identical manner to its unstable state, generating a first control pulse having a duration T each time the bistable multivibrator 32 is switched from one stable state to the other stable state at time instants t t t;,, t t etc.

The above-mentioned identity of the various circuits in the different embodiments allows many different variations of inill jection systems to be constructed using identical building blocks. Thus, a great variety of engines may be supplied with suitable injection systems in accordance with the needs of the particular engine. For example, the fourth embodiment is not necessarily restricted in application to use in rotary piston motors. It may for example be used in the operation of a sixcylinder combustion engine wherein the six injectors are divided into two groups of three injectors each, one group taking the place of injector 21 in the Figure, while the other takes the place ofinjector 22.

While the invention has been illustrated and described as embodied in an injection system using capacitive type storage means, it is not intended to be limited to the details shown, since various modifications, structural and circuit changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

We claim:

1. In an engine having an operating cycle, an electrically controlled fuel injection system, comprising, in combination, at least two injection means adapted to inject fuel sequentially at predetermined time instants in said operating cycle, each for a length of time dependent upon the duration ofan activa tion signal; means for furnishing first control signals at said predetermined time instants, said first control signals having a duration varying in response to at least one engine parameter; storage means adapted to furnish an additional control signal for each of said first control signals, the termination of each of said additional control signals following the termination of the corresponding first control signals in said operating cycle by a first time interval, the duration of said first time interval being a function of the duration of the corresponding first control signal; means for combining said first and additional control signals to form said activation signals in such a manner that the beginning of each of said activation signals is dependent upon the beginning of the corresponding first control signal and the end of each of said activation signals is dependent upon the termination of the corresponding additional control signal; and means for applying said activation signals to each of said injection means at the corresponding predetermined time instant.

2. A system as set forth in Claim 1, wherein said means for generating said first control signals comprise monostable control multivibrator means; and wherein said first control signals comprise first control pulses.

3. A system as set forth in Claim 2, wherein said additional control signals comprise additional control pulses.

4. A system as set forth in claim I, wherein the duration of said first time interval is proportional to the duration of the corresponding first control pulses.

5. A system as set forth in Claim 3, wherein the beginning of each of said additional control pulses substantially coincides with the termination of the corresponding first control pulse; and wherein said means for combining said first and additional control pulses comprise at least a first and second OR-gate, each having a first input adapted to receive said first control pulses and a second input adapted to receive said additional control pulses.

6. A system as set forth in claim 5, wherein said means for applying said activation pulses to each of said injection means at the corresponding time instant comprise switching means, one for each of said injection means, each adapted to permit the application of a signal to the corresponding injection means when operated; means for operating said switching means at said predetermined time instants; bistable circuit means adapted to be switched alternately to a first and second stable state by the closing of sequential ones of said switching means, further adapted to cause said mono-stable multivibrator to switch to the unstable state for each change of state of said bistable circuit means, said bistable circuit means also being adapted to generate a first bistable output signal when in said first stable state and a second bistable output signal when in said second stable state; and means for applying said first control pulse to said first OR gate in the presence of said first bistable output signal, and to said second OR gate in the presence of said second bistable output signal.

7. A system as set forth in Claim 6, wherein said means for applying said first and second control signals to said first and second OR gates respectively, comprise a first AND gate, adapted to receive said first bistable output signal and said first control signals, and generate a first AND output signal in the simultaneous presence of both of said signals; and a second AND gate adapted to receive said first control signals and said second bistable output signal, and to generate a second AND output signal in the presence of both of said signals.

8. A system as set forth in Claim 7, wherein said storage means comprise first circuit means adapted to store charge for the duration of said first AND output signal, and adapted to generate said additional control signal upon termination of said first AND output signal; and second circuit means adapted to store charge for the duration of said second AND output signal, and adapted to generate said additional control signal upon termination of said second AND signalv 9. A system as set forth in Claim 8, wherein said first circuit means comprise a first capacitor; and a first transistor adapted to permit charging of said first capacitor for the duration of said first AND signal; and wherein said second circuit means comprise a second capacitor; and a second transistor adapted to permit charging of said second capacitor for the duration of said second AND signal.

10. A system as set forth in Claim 9, also comprising first and second discharge means adapted to cause said first and second capacitor, respectively, to discharge at a constant current.

11. A system as set forth in Claim 10, wherein each of said first and second discharge means comprise first and second supply voltage lines; voltage divider means connected across said supply voltage lines; first transistor means having a base connected to said voltage divider means, an emitter having a load resistor, connected to said first supply voltage line, and a collector connected to said capacitor; and second transistor means, of opposite conductivity to said first transistor means,

having a base connected to said capacitor, an emitter connected to said second supply voltage line, and a collector, having a load resistor, connected to said first supply voltage line.

12. A system as set forth in Claim 6, comprising a first, second, third and fourth injection means, adapted to inject fuel in that order; also comprising first additional bistable circuit means adapted to be switched to a first and second bistable state by said first and third injection means respectively, and adapted to generate a first and second additional bistable output signal when in said first and second bistable states, respectively; a first additional AND gate, adapted to receive said first additional bistable output signal and said activation signal; a second additional AND gate adapted to receive said second additional bistable output signal and said activation signal; second additional bistable circuit means adapted to be in a first bistable state in response to operation of said second switching means, and in a second bistable state in response to operation of said fourth switching means, and further adapted to generate third and fourth additional bistable output signals when in said first and second bistable states, respectively; a third additional AND gate adapted to receive said third additional bistable output signal and said activation signal; and a fourth additional AND gate adapted to receive said fourth additional bistable output signal and said activation signal, said first, third, fourth and second injection means being activated in response to the output signals from said first, second, third and fourth additional ANDgates, res ectively.

13. A system as set forth in Claim ,wherein said engine has two injection means; and wherein said engine also has means for generating three synchronization signals, equally spaced throughout said operating cycle; and wherein said means for applying said activation signals to each of said injection means at the corresponding predetermined time instants comprises means for supplying said synchronization signals alternately to each of said two injection means.

14. A system as set forth in Claim 6, also comprising differentiating means responsive to the change of state of said bistable means and adapted to generate signals for switching said monostable multivibrator.

15. A system as set forth in Claim 6, wherein the periods of operation and non-operation of each of said switching means are approximately equal in each operating cycle.

16. A system as set forth in Claim 1, for at least six injection means; wherein said engine has at least six cylinders, one corresponding to each of said injection means; and wherein pairs of said injection means, belonging to cylinders which are adjacent in the operating cycle, are activated simultaneously. 

